Folic acid is an essential vitamin. The measurement of folic acid levels is almost always prescribed at the same time as that for vitamin B12, particularly for people with a form of anemia characterized by abnormally large red blood cells (macrocytic anemia) or with neuropathy (nerve cell damage). Since flour products sold in North America must be fortified with folic acid, the consumption of such products helps provide an adequate supply of the vitamin, with rare exceptions. The measurement of folic acid and vitamin B12 levels allows an indirect assessment of the nutritional status of individuals in groups likely to have a deficiency (e.g. malnutrition in elderly people living alone or struggling with alcoholism, chronic intestinal malabsorption, etc.). It also makes it possible to evaluate the effectiveness of a prescribed treatment for vitamin B12 or folic acid deficiency.
A high folic acid serum level is not significant. However, a lower folic acid level accompanied by other signs of macrocytic anemia is a confirmation of a folic acid deficiency.
Folic acid serum levels depend on a person’s recent dietary intake. In some situations, a normal level may not reflect the actual amount of folic acid available to cells. If needed, it is preferable to establish the folic acid level in red blood cells (erythrocyte folates).